Fspl and vimentin are not universal markers of EMT programs in the MMTV-PyMT breast cancer model.

a, Schematic illustration showing the two criteria for a lineage tracing system to faithfully report EMT. b, c, Tumour sections from Snai1YFF/+;MMTV-PyMT animals were stained with DAPI as well as for cytokeratin (an epithelial marker) and either Fsp1 or vimentin together with YFP (b), which marks Snail-expressing cells, or the EMT transcription factor Zeb1 (c). Error bars represent mean ± s.d. Expression of Snail (a, green) and Zeb1 (b, green) is seen in cells that exhibit no evidence of Fsp1 or vimentin expression (red) as indicated by the arrows. Quantifications are shown in the right panels. A minimum of three different microscopic fields were counted per tumour for each marker combination. Scale bars, 20 μm.